Calcite

Terlingua-type calcite. This blue fluorescence is actually phosphorescence.
The energy of the 254 nm (short wave) UV is believed to be absorbed by cerium
and then photochemically transferred to europium, which fluoresces blue. Since
there is a visible delay at the start of the fluorescence (first pink, then
blue) and a long lived phosphorescence, we should call this phosphorescence
instead of fluorescence.

Under a somewhat shorter wavelenght of UV (350 nm peak) the pinkish
fluorescence turns to an almost straw-yellow colour. This is probably caused
by the blue fluorescence/phosphorescence that is starting to show. Removing
the UV-source reveals a short-lived blue phosphorescence.

This is the typical fluorescence under 366 nm UV. The activator probably is
manganese with some co-activator, most likely one or more of the rare earth
elements. Photo was taken under a well-filtered blacklight (true blacklight
with wood-glass mantle).